1. Field of the Invention
The invention relates to a method for briquetting metal chips and a briquetting press for carrying out the method.
2. Description of the Invention
DEA-40 39 788 discloses briquetting presses that have at least one pressing ram disposed in a pressing sleeve to press metal chips in the form of briquettes. A stamper is used to feed the metal chips to a metering device disposed radially in relation to the pressing sleeve. The process flow is as follows:
advancing the stamper, filling and closing the pressing sleeve,
advancing the pressing ram and feeding the metal chips into the pressing section of the pressing sleeve,
applying pressure to the metal chips with at least one pressing ram until a final pressure Pmax or a required pressure Preq is attained,
optionally, retracting a second pressing ram and expelling the completed pressed article as a briquette using the first pressing ram, and
retracting the first pressing ram and, optionally, advancing the second pressing ram into the initial position.
The aforedescribed, optionally double-acting, briquetting presses, unlike conventional briquetting presses, produce a pressed article with a particularly high densification approximating the intrinsic density of the metal, and also have a high throughput, thereby optimally achieving both a high density and a high efficiency. In contrast to single-sided presses, significantly longer briquettes can be produced, because the stroke lengths, in order to be manageable, have to stay within practical limits, as determined by the machine tool and the manufacturing environment.
EP-A-0 367 859 also describes a method and a briquetting press for making briquettes having dimensional stability from pressed material in the form of chips, fiber, dust, and lamellar material. The material to be pressed is hereby fed to a precompacting plunger and precompacted in a receiving chamber and thereafter further compacted in a forming box by a press plunger which moves perpendicular to the precompacting plunger. According to this invention, by exactly determining the end position of the press plunger and the precompacting plunger, respectively, variations in the material to be pressed can be almost entirely eliminated, so that the intended power of the press can be utilized with a high efficiency.
However, the results from these technical teachings can not be applied to axially-aligned, double-acting briquetting presses.
U.S. Pat. No. 5,326,511 also teaches a solution similar to that of the previous reference. However, even when taking into account all the features of this type of presses which operate with a precompacting plunger and a press plunger in mutually perpendicularly disposition, the prior art presses do not suggest an obvious solution that can be adapted to pressing rams operating in opposing directions in a pressing sleeve, since this arrangement represents a completely different type of press with an entirely different operating characteristic.
Indeed, a double-acting briquetting press with pressing rams operating in a pressing sleeve cannot easily produce pressed articles in the form of briquettes with a workable and acceptable length and also a small manufacturing tolerance. Disadvantageously, the maximum possible fill volume in the pressing sleeve over the length of the briquette can hence not be fully utilized even if maximum pressing power is applied.
It is an object of the invention to provide a method that provides a greater mass throughput of metal chips to be pressed by utilizing the maximum usable nominal length of the briquette, while maintaining the aforedescribed, generally advantageous functional process flow. This is achieved with an improved metering process of the metal chips which results in a maximum fill volume in the pressing sleeve. It is also an object to provide a briquetting press with suitable technical means for carrying out the method so as to improve metering of the metal chips.
The invention as a whole is intended to produce dimensionally stable briquettes.
The invention is limited to a type of press with only a single pressing sleeve with an opening for the radially disposed metering device with a stamper, which simultaneously functions as a closing member for the opening in the pressing sleeve, as well as two pressing rams with piston rods guided in this pressing sleeve and a stand, frame or housing adapted to receive these components and associated pressure generators.
According to the invention, a method for briquetting of metal chips in a briquetting press is described. The briquetting is done by applying pressure to an article with two pressing rams, which operate in opposite directions. The rams are disposed in a pressing sleeve into which the metal chips are supplied via a metering device by a stamper, which is arranged in radial disposition on the pressing sleeve. Once the stamper fills the pressing sleeve with metered metal chips, the pressing sleeve is closed. Both pressing rams are advanced and feed the metal chips into the pressing section of the pressing sleeve. Pressure is then applied to the metal chips with both pressing ram until a final pressure Pmax or a required pressure Preq is attained. The pressing rams are then retracted, and the completed pressed article is expelled as a briquette. The rams are returned to their initial position. When the pressure Pmax/Preq is applied by the rams, the attained length (Lact) of the pressed article is measured with a measurement device, and this value is compared with a nominal value (Lnom). A difference in the two values is determined (xcex94). Further, the quantity/mass of a metal chips to be fed from the metering device is determined from this difference value (xcex94) according to the nominal length (Lnom) of the pressed article and, subsequently, the fill quantity is adjusted in the metering device and the corresponding quantity/mass is supplied by the stamper. The process steps of the process flow loop may be repeated again, and pressure may be applied to the metal chips collectively with the pressing rams until the final pressure Pmax and/or the required pressure Preq is attained so as to thereby obtain the nominal value (Lnom) of the length of the briquettes.
It is also contemplated to use an integrated measurement device for determining and/or adjusting the lengths of the briquettes (Lact and Lnom, respectively). The measurement device may be integrated on a piston rod of the pressing ram. An electronic logic module is used for determining the length of the briquettes from the relative position of the pressing ram (1, 2) with the integrated measurement device (5, 6) according to the relationship (Lnom/act=S1xe2x88x92S2). The use of an electronic logic module activates in the metering device a command to increase the metered amount, if it is determined that the actual length Lact of the briquettes is smaller than the nominal value Lnom. It is also possible to activate a command to decrease the metered amount, if it is determined that the actual length Lact of the briquettes is greater than the nominal value Lnom. Further, it is contemplated that the electronic control circuit includes actuators for setting the process data required by the present process, such as the metered quantity, density of the pressed article, length of the pressed article and pressing power. Accordingly, a briquetting press for carrying out the method includes components that carry out the functional operations of the machine, such as a pressing sleeve with an opening for the radially disposed metering device with a stamper which operates also as a closing member for the opening in the pressing sleeve, two pressing rams with piston rods guided in the pressing sleeve, and a stand, frame or housing receiving these components as well as associated pressure generators. Each of the piston rods of the pressing rams is provided with a measurement device. A control circuit for affecting metering of the metal chips as a function of the briquette lengths (Lnom/Lact), as determined by the measurement device, is provided between the measurement device and the metering device, and the control circuit includes actuators and a logic module for controlling the process flow according to the relationship between the briquette length and the metered quantity/mass.